Clinical Characteristics and Disease Severity Among Infants With SARS-CoV-2 Infection in Montreal, Quebec, Canada

With more than 40 million cases of confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection worldwide, the clinical presentation and risk factors for disease severity among adults and children have now been well described.1 SARS-CoV-2 is the virus that causes coronavirus disease 2019. However, little remains known about disease manifestation and severity of illness in infants.2 Although infants are at higher risk of severe disease and complications from other common viral respiratory pathogens (influenza, respiratory syncytial virus), it is not yet clear whether this is the case with SARS-CoV-2 infection because few series describing outcomes in infants have been published.3,4 The objective of this study was to describe the manifestations and severity of disease among infants with SARS-CoV-2 infection.


Introduction
With more than 40 million cases of confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection worldwide, the clinical presentation and risk factors for disease severity among adults and children have now been well described. 1 SARS-CoV-2 is the virus that causes coronavirus disease 2019. However, little remains known about disease manifestation and severity of illness in infants. 2 Although infants are at higher risk of severe disease and complications from other common viral respiratory pathogens (influenza, respiratory syncytial virus), it is not yet clear whether this is the case with SARS-CoV-2 infection because few series describing outcomes in infants have been published. 3,4 The objective of this study was to describe the manifestations and severity of disease among infants with SARS-CoV-2 infection.

Methods
This case series describes all infants younger than 1 year with laboratory-confirmed SARS-CoV-2 infection (confirmed a by positive reverse transcriptase-polymerase chain reaction result) who were diagnosed or treated at Centre Hospitalier Universitaire Sainte-Justine (CHU-SJ), Montreal, Quebec, Canada, between February 14 and May 31, 2020. The study was approved by the CHU-SJ research ethics board with the requirement for informed consent waived owing to the retrospective nature of the study. Clinical features and severity of disease were compared between infants younger than 3 months chronologic age (younger infants) and infants 3 to 12 months old (older infants). Disease severity was defined using the widely used criteria from Dong et al. 5 The Appropriate Use and Reporting of Uncontrolled Case Series in the Medical Literature guideline (https://www.ajo.com/article/ S0002-9394(10)00690-2/fulltext) was the reporting guideline for this case series. Variables were compared using the Wilcoxon rank sum or Fisher exact test where appropriate, using a 2-sided α level, with P < .05 considered statistically significant. Statistical analyses were performed with Stata, version 12.1 software (StataCorp).

Results
Of 1165 infants who were tested for SARS-CoV-2 infection at CHU-SJ during this 2020 study period, 25 (2%) had confirmed positive results, and 8 of those with positive results (32%) required hospitalization. Two additional infants with SARS-CoV-2 positive results were transferred directly to CHU-SJ for hospitalization and are included in the analysis. Of those 27 infants, 15 (56%) were male, the median age was 89 days (interquartile range [IQR], 34-193 days), and 7 (26%) had comorbid conditions. Clinical characteristics and laboratory and imaging findings of the 10 hospitalized infants are described in Table 2. Three of the hospitalizations (30%) were determined to be non-SARS-CoV-2related (urinary tract infection, n = 2; intussusception, n = 1). Disease was again mild in most (7 [70%]) of hospitalized patients; none of the infants required supplemental oxygen. The single admission to the intensive care unit was for a non-SARS-CoV-2-related infection (urosepsis from E coli). SI conversion factors: To convert white blood cell, neutrophil, and lymphocyte counts to ×10 9 /L, multiply by 0.001; platelet count to ×10 9 /L, multiply by 1.0; ALT to μkat/L, multiply by 0.0167; and CRP to mg/L, multiply by 10.
a The characteristics of the analyzed population include those of the 2 patients from other hospitals; however, the hospitalization rate should not be compared with the rate of hospitalization reported in the literature. 6 b P < .05 was considered statistically significant.
c Family contact was defined by a contact with a symptomatic or laboratory-confirmed family member.

Discussion
In this case series report, we describe the first series, to our knowledge, of infants with SARS-CoV-2 infection reported from Canada. Our findings are consistent with previous series describing infants who present with mainly fever, mild disease, and no need for mechanical ventilation or intensive care treatment. 3,4 However, the proportion of hospitalization among the 25 infants tested at our center (32%) was lower than that reported by the US Centers for Disease Control and Prevention (62%) among 95 infants with known hospitalization status. 6 We suspect this higher risk may reflect practice in the early phase of the pandemic, when in the absence of data, infants may have been hospitalized out of an abundance of caution. These results suggest that no additional SARS-CoV-2-related investigations may be necessary for the majority of infants.
Our study is limited by its small sample size, retrospective observational study design, and testing indications that followed public health guidelines. As a result, we have included only symptomatic infants in our analysis and potentially overestimate the severity of illness.